package com.c3stones.filter;

import java.io.IOException;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

import lombok.extern.slf4j.Slf4j;

/**
 * CSRF过滤器
 * 
 * @author CL
 *
 */
@Slf4j
@Component
@ConfigurationProperties(prefix = "security.csrf")
@WebFilter(filterName = "CsrfFilter", urlPatterns = "/*")
public class CsrfFilter implements Filter {

	/**
	 * 过滤器配置对象
	 */
	FilterConfig filterConfig = null;

	/**
	 * 是否启用
	 */
	private boolean enable;

	public void setEnable(boolean enable) {
		this.enable = enable;
	}

	/**
	 * 忽略的URL
	 */
	private List<String> excludes;

	public void setExcludes(List<String> excludes) {
		this.excludes = excludes;
	}

	/**
	 * 初始化
	 */
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		this.filterConfig = filterConfig;
	}

	/**
	 * 拦截
	 */
	@Override
	public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
			throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) servletRequest;

		// 不启用或者已忽略的URL不拦截
		if (!enable || isExcludeUrl(request.getServletPath())) {
			filterChain.doFilter(servletRequest, servletResponse);
			return;
		}

		String referer = request.getHeader("Referer");
		String serverName = request.getServerName();

		// 判断是否存在外链请求本站
		if (null != referer && referer.indexOf(serverName) < 0) {
			log.error("CSRF过滤器 => 服务器：{} => 当前域名：{}", serverName, referer);
			servletResponse.setContentType("text/html; charset=utf-8");
			servletResponse.getWriter().write("系统不支持当前域名的访问！");
		} else {
			filterChain.doFilter(servletRequest, servletResponse);
		}
	}

	/**
	 * 销毁
	 */
	@Override
	public void destroy() {
		this.filterConfig = null;
	}

	/**
	 * 判断是否为忽略的URL
	 * 
	 * @param urlPath URL路径
	 * @return true-忽略，false-过滤
	 */
	private boolean isExcludeUrl(String url) {
		if (excludes == null || excludes.isEmpty()) {
			return false;
		}
		return excludes.stream().map(pattern -> Pattern.compile("^" + pattern)).map(p -> p.matcher(url))
				.anyMatch(Matcher::find);
	}
}